NO2- Lewis structure

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NO2- Lewis structure
NO2 Lewis structure

The NO2 Lewis structure contains one single bond and one double bond, with nitrogen in the center, and two oxygens on either side. The left oxygen atom has three lone pairs, the right oxygen atom has two lone pairs, and the nitrogen atom has one lone pair.

Plus, there is a negative (-1) charge on the left oxygen atom.

Steps

By using the following steps, you can easily draw the NO2 Lewis structure.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

  • Let’s calculate the total number of valence electrons

We know that… nitrogen is a group 15 element and oxygen is a group 16 element. Hence, nitrogen has five valence electrons and oxygen has six valence electrons.

Now NO2 has one nitrogen atom and two oxygen atoms.

So the total number of valence electrons = valence electrons of nitrogen atom + (valence electrons of oxygen atom × 2)

And NO2 has a negative (-1) charge, so we have to add one more electron.

Therefore, the total number of valence electrons = 5 + 12 + 1 = 18

  • Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for nitrogen and oxygen as follows:

Electronegativity value of nitrogen = 3.04
Electronegativity value of oxygen = 3.44

Obviously, nitrogen is less electronegative than oxygen. Hence, assume that nitrogen is the central atom.

So now, put nitrogen in the center and oxygens on either side. And draw the rough skeleton structure for the Lewis structure of NO2 something like this:

Skeleton structure for NO2 Lewis structure

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since nitrogen is surrounded by two oxygens, use four electrons to show two chemical bonds as follows:

Two chemical bonds shown between atoms

#3 Mark lone pairs

As calculated earlier, we have a total of 18 valence electrons. And in the above structure, we have already used four valence electrons. Hence, fourteen valence electrons are remaining.

Two valence electrons represent one lone pair. So fourteen valence electrons = seven lone pairs. Also, we have one unpaired electron.

Note that both (nitrogen and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are oxygens, so each oxygen will get three lone pairs. And the central atom (nitrogen) will get one lone pair.

So the Lewis structure of NO2 looks something like this:

Lone pairs marked on NO2 Lewis structure

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (nitrogen) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

#4 Complete octet on central atom

Remember that nitrogen is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now nitrogen already has six valence electrons. Hence, nitrogen needs two more valence electrons to complete its octet.

So convert one lone pair from one oxygen atom to make a new bond with the nitrogen atom. And then, the Lewis structure of NO2 looks something like this:

Lone pair of right oxygen is converted, and octet is completed on atoms

In the above structure, you can see that the octet is completed on the central atom (nitrogen), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

#5 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

  • For nitrogen atom

Valence electrons = 5
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 5 – 2 – ½ (6) = 0

  • For left oxygen atom

Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 6 – 6 – ½ (2) = -1

  • For right oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of NO2 looks something like this:

Formal charges are calculated, and got the most stable Lewis structure of NO2

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of NO2.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

Now NO2 is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of NO2 looks something like this:

NO2 Lewis structure showing a negative (-1) charge

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Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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